1. Field of the Invention
The present invention relates in general to the incineration of hazardous wastes and, in particular, to the incineration of hazardous wastes using closed cycle combustion and ash vitrification.
2. Description of the Related Art
Incineration is the principal means employed for the permanent destruction of hazardous organic wastes. The incinerator destruction efficiency of some organic hazardous wastes must be on the order of 99.9%. Other organics must be destroyed to an efficiency of 99.99%, and still others such as dioxins must be destroyed to an efficiency of 99.9999%. Under some conditions, hazardous wastes can be burned in conventional boilers. However, these boilers are not always well suited to achieve the high destruction efficiencies required. For example, the carbon conversion efficiency of a coal-fired boiler usually will not exceed much more than about 99.6%. Conventional incinerators designed for the explicit purpose of destruction of hazardous organic wastes include simple refractory enclosures designed to burn liquid wastes (liquid injection furnaces), rotary kilns, multiple rotary hearths, and fluidized bed incinerators.
All known hazardous waste incineration processes are open cycle processes with respect to the gas phase. Air is used as the oxidant and consequently, flue gas, i.e., the products of the reaction plus nitrogen, must be exhausted from the process and vented to the atmosphere. One consequence of this situation is the fact that if the destruction of the hazardous waste is not completed to the prescribed extent, e.g., 99.99%, then the untreated hazardous waste is released directly to the atmosphere where it can endanger public health. This situation is complicated further by the fact that no economically viable continuous monitoring instrumentation exists which can measure the emission rate of these hazardous species on a full time basis. Adequate performance of the incinerator must be "inferred" based upon periodic spot tests of the incinerator. These spot tests are used to define a proper set of operating conditions for that incinerator to "insure" the destruction of the specific hazardous wastes.